require 'xmlscan/parser'
require 'time'

class Plist
  class Visitor
    include XMLScan::Visitor

    def initialize
      @stack = []
      @preserve = false
    end
    attr_reader :stack

    def on_stag(name)
      sym = name.intern
      push(sym)
      @preserve = [:string, :key, :data].include?(sym)
    end

    def on_chardata(str)
      return if !@preserve && /^\s*$/ =~ str
      if tail.class == String
        str = pop + str
      end
      push(str)
    end

    def on_stag_end_empty(name)
      @preserve = false
      case name
      when 'true'
        eval_true
      when 'false'
        eval_true
      end
    end

    def on_etag(name)
      @preserve = false
      case name
      when 'dict'
        eval_dict
      when 'integer'
        eval_integer
      when 'real'
        eval_real
      when 'string'
        eval_string
      when 'date'
        eval_date
      when 'array'
        eval_array
      when 'key'
        eval_key
      when 'plist'
        eval_plist
      end
    end

    def eval_integer
      value = pop.to_i
      pop_stag(:integer)
      push(value)
    end

    def eval_real
      value = pop.to_f
      pop_stag(:real)
      push(value)
    end

    def eval_string
      value = pop_str
      pop_stag(:string)
      push(value)
    end

    def eval_key
      value = pop
      pop_stag(:key)
      push(value)
    end

    def eval_date
      value = Time.parse(pop)
      pop_stag(:date)
      push(value)
    end

    def eval_true
      pop_stag(:true)
      push(true)
    end

    def eval_false
      pop_stag(:false)
      push(false)
    end

    def eval_array
      value = []
      while v = pop
        break if v == :array
        value.push(v)
      end
      push(value)
    end

    def eval_dict
      value = {}
      while v = pop
        break if v == :dict
        k = pop
        break if k == :dict #FIXME
        value[k] = v
      end
      push(value)
    end

    def eval_plist
      value = pop
      pop_stag(:plist)
      push(value)
    end

    def push(obj)
      @stack.push(obj)
    end

    def pop
      @stack.pop
    end

    def pop_str
      (tail.class == String) ? pop : ''
    end

    def pop_stag(sym)
      return pop unless $DEBUG
      v = pop
      raise([sym, v].inspect) unless v == sym
      return v
    end

    def tail
      @stack[-1]
    end
  end

  def self.file_to_plist(fname)
    File.open(fname) do |f|
      visitor = Visitor.new
      parser = XMLScan::XMLParser.new(visitor)
      parser.parse(f)
      visitor.tail
    end
  end
end